Re: how does the battery get charged
The charging device, the stator is up under the flywheel. It's excited by permanent magnets glued to the flywheel. AC comes out of it, which is rectified into 12 volt DC by the rectifier Lubosleftboot identified.<br /><br />It's rarely troublesome, but does go bad sometimes. Usually something causes it, like a battery attached backward, running without the battery connected, or loose battery connections. This usually kills the rectifier first though.<br /><br />The stator also supplies power to the ignition system, but via a separate set of coils.<br /><br />To test if the charging system is working properly, check the voltage at the battery before and after you start the engine. It should go up when running, though you may have to rev it up some. Do that in gear; it's not a good idea to rev 2-strokes unloaded.<br /><br />A dead tach sometimes indicates charging system problems, because it takes it's signal from the stator's charge coils.
<br /><br />By far the biggest problem with blown charging systems comes from using wing nuts on the battery. If you've got them, tighten them with pliers or replace them with nuts.
